This invention relates generally to needle bearings for rotatably supporting the end of a shaft in a bearing cup and specifically to a wear reduction arrangement which causes the needle bearings to positively circumferentially migrate with respect to the shaft and bearing cup to avoid excessive wear.
In the typical Cardan type composite universal joint, a generally cross-shaped spider includes four legs or trunnions each of which is rotatably supported in a bearing cup by a series of needle bearings circumferentially spaced therearound. The bearing cups are arranged in two axially aligned pairs, each pair included on one of a pair of 90.degree. displaced yoke members. Each yoke member is in turn mounted to a shaft member. Typically, each bearing cup includes a pair of washers which float freely in a lubricant contained therein, each washer being proximate to the ends of the circumferentially spaced needle bearings. Each trunnion generally rotates within the cup over an arc of only one or two degrees. As a consequence, each needle bearing has a fairly constant center of oscillation with respect to the trunnion and the bearing cup which leads to excessive wear or brinneling thereof. It is, therefore, desirable to positively induce a circumferential migration of the needle bearings to randomly vary the centers of oscillation thereof.
Prior art devices designed to induce migration of the bearings generally include one or more ring members which are continually biased against the ends of the needle bearings, placing a continuous axial load thereon. During torque variations in the operation of the joint, a slight braking effect on the needle bearings occurs, causing a change in the center of oscillation thereof. Besides involving elements not normally found in the universal joint, such structures involve obvious problems of increased friction and wear on the ends of the needle bearings.